According to USDA ARS hybridization occurs first
"Many experts expected that the farther from a tropical climate AHBs spread, the more they would interbreed with EHBs. But it appears that interbreeding is a transient condition in the United States, according to ARS entomologist Gloria DeGrandi-Hoffman. She is research leader at the Carl Hayden Bee Research Center in Tucson, Arizona, and ARS national coordinator for AHB research.
"Early on, we thought the mixing would reach a steady state of hybridization, because we knew the two groups of bees can easily interbreed and produce young," DeGrandi-Hoffman says. "But while substantial hybridization does occur when AHBs first move into areas with strong resident EHB populations, over time European traits tend to be lost." "
They are still considered a hybid with dominant African traits
"Finally, some African traits are genetically dominant, such as queen behavior, defensiveness, and some aspects of foraging behavior. This doesn't mean that EHB genes disappear, but rather that hybrid bees express more pure African traits. The persistence of some EHB genes is why the invading bees are still considered Africanized rather than African, regardless of trait expression, she points out."
The early opinions on the transition as AHB spread North has been overcome by reality.
"Some experts predicted the bees would spread throughout the country; others thought they'd reach only as far north as the latitude of Houston. Most expected there would be a southern zone where AHBs would predominate, a northern zone where EHBs would maintain a climatic advantage, and a large transitional zone between the two. And everyone expected AHBs to spread across the southernmost tier of states. But, as of January 2004, AHBs have been found only in southern California, Arizona, New Mexico, Nevada, and Texas, as well as Puerto Rico and the U.S. Virgin Islands."
The most interesting and least known is the correlation between rainfall, temperature and the spread or not of AHB.
"Why AHBs haven't progressed eastward into Louisiana—though they were expected there years ago—is a mystery. So ARS entomologist José D. Villa began looking at factors that might correlate with where AHBs have spread. It isn't just minimum winter temperature that limits AHB spread, as many believed, says Villa, who is in the ARS Honey Bee Breeding, Genetics, and Physiology Research Unit in Baton Rouge, Louisiana.
"What immediately jumped out at me was the correlation with rainfall," he says. "Rainfall over 55 inches, distributed evenly throughout the year, is almost a complete barrier to AHB spread."
Total annual rainfall alone isn't a barrier; AHBs have been found in areas of the Tropics with higher rainfall. But in areas with high rainfall distributed throughout the year, Villa's pattern of AHB spread fits perfectly.
Villa is quick to point out that this is simply a mathematical correlation and not proof of cause and effect. But, he says, "you do find that 55-inches-of-rainfall point right at the edge of where AHBs stopped moving east about 10 years ago." He's planning experiments that may uncover the behavioral or physiological mechanism that explains why.
How much farther AHBs may spread is still unknown. But if you apply the 55-inches-of-rainfall limit, there are still niches that the bees may fill, mainly in southern California. Southern Florida would be hospitable to the bees given its temperature and rainfall, but regulatory vigilance could keep them out, since the area isn't contiguous with the other areas of AHB spread. Alabama, northern Florida, Louisiana, and Mississippi are unlikely to be troubled by AHBs if the 55-inches-of-rainfall barrier holds."
I use these quotes with USDA ARS permission as I am teaching the AHB classes at Florida Bee College and the authors provided it.